In recent years, increasingly-prevailing LED light bulbs include therein LED modules in sealed globes. An LED module is configured so that an LED substrate has thereon an LED chip and the LED chip is composed of an assembly member sealed by translucent resin.
When an LED chip is supplied with electric power and emits light, the LED chip has an increased temperature due to electric power not contributing to the light emission from the LED chip. In this case, when the LED chip has insufficient heat dissipation measures, the LED chip fails or is broken. To prevent this, an LED module (LED package) having improved LED chip heat dissipation has been suggested (see for example Patent Publication 1).
The following section will describe an LED module disclosed in Patent Publication 1 with reference to FIG. 9. FIG. 9 is a cross-sectional front view illustrating an example of a conventional LED module.
As shown in FIG. 9, the LED module disclosed in Patent Publication 1 is configured so that one face of substrate 1 consisting of silicon or ceramic for example includes concave section 1a having a bottom section and a slope face. Concave section 1a has, at the center thereof, installation pattern 3. Installation pattern 3 has thereon LED chip 2 provided via conductive paste (not shown).
The slope face of concave section 1a has thereon wiring pattern 5. Wiring pattern 5 is connected to LED chip 2 by metal thin wire 6. LED chip 2, wiring pattern 5, and metal thin wire 6 are sealed by translucent resin 4. Resin 4 is added with fluorescent substance.
Through hole 1b is formed from the center of concave section 1a of substrate 1 to an opposite face of substrate 1. Through hole 1b has connecting section 7. Heat dissipation pattern 8 is provided at an opposite face of substrate 1 to surround through hole 1b. Heat dissipation pattern 8 and installation pattern 3 are connected via connecting section 7 provided in through hole 1b. As a result, the conventional LED module is configured so that heat generated in LED chip 2 is sequentially transmitted through conductive paste, installation pattern 3, connecting section 7, and heat dissipation pattern 8 and is dissipated to the exterior via heat dissipation pattern 8.
However, since substrate 1 of the LED module uses high-cost ceramic having superior heat dissipation, an increased cost is required for an LED light bulb including an LED module.
In order to suppress the cost increase of an LED light bulb, one approach is considered to use low-cost glass for example for substrate 1 of the LED module.
However, since glass has a low thermal conductivity, when glass is used for substrate 1 of the LED module, a disadvantage has been caused in which heat generated in LED chip 2 cannot be sufficiently dissipated.
On the other hand, even when ceramic having superior heat dissipation is used to form substrate 1 of the LED module, an increase in a light emission amount of LED chip 2 causes an increase in heat generated in LED chip 2. Thus, even the use of ceramic having superior heat dissipation may fail to provide sufficient heat dissipation of heat generated in LED chip 2.
Thus, an LED substrate, an LED module, and an LED light bulb have been conventionally desired that provide superior heat dissipation with a low cost.